Photoresistor swell control for a musical instrument



May 19, 1970 w. J. ANDERSON ETA-L 3,513,247

'PH OTORESISTOR SWELL CONTROL FOR A MUSICAL INSTRUMENT Filed May 2, 1967ALBERTO E. KNIERKAMP v US. Cl. 841.18

United States Patent 3,513,247 PHOTORESISTOR SWELL CONTROL FOR A MUSICALINSTRUMENT Walter J. Anderson, Elgin, and Alberto E. Kniepkamp, Chicago,Ill., assignors to Chicago Musical Instrument Company, a corporation ofDelaware Filed May 2, 1967, Ser. No. 635,493 Int. Cl. Gh 1/02 3 ClaimsABSTRACT OF THE DISCLOSURE A swell control for an electrical musicalinstrument embodies a photoresistor coupling the tone signal output tothe signal reproducing means of the instrument. An incandescent lightbulb is energized by direct current of low voltage to emit light theluminous intensity of which is insuflicient per se to excite thephotoresistor. The bulb is selectively movable in a housing and disposedto emit light the luminous intensity of which selectively energizes thephotoresistor to control conduction of the signal output to thereproducing means and secure variation in the volume of sound thereat.

The herein disclosed preferred embodiment of the invention ischaracterized by interrelated coactive elements that can be included ina swell pedal assembly and readily incorporated in circuit with the tonesignal output system and the electroacoustic signal reproducing means ofan electrical musical instrument and operated by the player to controlthe decibel level of sound at the reproducing means. The principalfeature of the invention is the use of light the luminous intensity perse of which is insuflicient to excite a photoresistor coupling betweenthe signal output system and the electroacoustic reproducing means ofthe instrument, which said light is emitted by an incandescent bulbenergized by direct current oflow voltage. To utilize the light toexcite the photoresistor means the bulb is selectively movable in alinear direction between minimum and maximum extremes to cause variationin exciting brightness of light falling on the photoresistive means andproportional variation in the resistance and conductivity thereof andaccompanying conduction of the signal output to the reproducing meansand control of the decibel level of sound thereat.

An important feature of the invention is a photoelectric volume controlsystem wherein one or any desired number of tone signal channels may beconnected in circuit with respective reproducing systems and a commonlight signal source for conversion thereof from a minimum conductiveelectrical state to a selected variable conductive electrical state andconversely by photoelectric means in each of said channels all of whichare common to a single light source and may be activated and deactivatedby means such as the expression pedal of an organ or equivalent meansfor varying the relationship of the light source to the photoelectricmeans in the respective tone signal channels.

Other objects and advantages are:

The provision of an expression control which is highly dependable inoperation, requires infrequent servicing; eliminates transient noisesinherent in prior systems employing potentiometers, rheostats andsimilar devices for making and breaking circuit between a tone signalsource and a reproducing system; is simple and may be economicallymanufactured, and is of a general construction enabling use thereof as aself-contained part of the expression pedal assembly of an organ andrequires no change mechanically or otherwise in adapting it to thesignal output circuit of an electric or electronic organ or othersimilar electrical musical instrument.

3,513,247 Patented May 19, 1970 The invention consists substantially inthe construction, combination, location and relative arrangement ofparts and the method employed in connection therewith, all as will bemore fully hereinafter set forth, as shown by the accompanying drawingand finally pointed out in the appended claims.

FIG. 1 is a view partly in section and partly in elevation of oneexemplified embodiment of the invention.

FIG. 2 is a view in longitudinal section of the light responsiveassembly showing the light source in its projected position relative tothe light responsive device.

FIG. 3 is a perspective view of the light responsive device, the lightsource and the mounting board therefor showing the light source in itsprojected position.

FIG. 4 is a schematic view of one exemplified embodiment of theinvention.

FIG. 5 is a view similar to FIG. 4 showing another exemplifiedembodiment of the invention.

FIG. 6 is a view similar to FIG. 4 showing a still further exemplifiedembodiment of the invention.

FIG. 7 is a detail sectional view showing the light source couplingmeans and interrelated guide rail.

In FIG 4, A is any well-known electric or electronic organ, the tonesignal output of which has a preamplifier B, which, in turn, is coupledto a power amplifier D and associated electroacoustic transducer F via alight responsive device comprising a photoresistor C which may be of thetype manufactured by or for General Electric Company of the UnitedStates'of America and identified as No. 65-15-1885GEB430G. Coactive withthe light responsive device and mounted for reciprocal motion relativethereto is a light source consisting of an incandescent bulb 34 whichmay be of the type identified as No. 1819, also manufactured by or forsaid General Electric Company. The bulb is connected to a battery S, thevoltage being relatively low in that only a minimum of light is requiredto obtain maximum conduction of photoresistor C, i.e., lowest resistancethereof; about on the order of 500 ohms when light of maximum luminousintensity falls thereon, the resistance increasing to several megohmswhen no light of exciting intensity strikes the photoresistor.

The resistance R of photoresistor C has one end coupled to the output ofpreamplifier B by a circuit lead wire W, the opposite end of theresistance connecting to ground through a 10K resistor R1, and as shown,a circuit lead wire W1 couples amplifier D to the junction point Pbetween resistance R and resistor R1.

When the light bulb 34 is moved a predetermined maximum distance awayfrom the light responsive device as would be the case where theexpression pedal of an organ is in a full Off condition, light from thebulb 34 is of insufficient luminous intensity to have any effect onresistance R, which is non-conductive and functions completely toprevent transmission of tone signal energy to amplifier D.

Like parts in the several figures of the accompanying drawing will bearlike reference numerals and characters.

In carrying the invention into practice, use is made of a pedalexpression assembly shown in detail in FIG. 1 as comprising a rigidhorizontally disposed base plate 10 having at its rear end a verticalbracket 11 on which a foot pedal 12 is mounted for vertical tiltingmotion about a bushing 12 through which passes a supporting shaft 12b.The pedal consists of a longitudinal rigid metallic plate 14 faced atits upper surface with resilient material 15. Integral with bracket 11is a stop extension 11a disposed and arranged to limit pivotal motion ofthe pedal from a full Off to a full On condition, said extension havinga resilient stop bumper 17 adapted to freely engage the rear end ofplate 14. Loosely encircling the bushing 12 is a steel coil spring 18having a long extremity 19 attached 3 at to plate 14 and a shortextremity 21 attached at 22 to said bracket 11, the function of thespring being to cause the convolutions thereof to resiliently grip thebushing-clutchlike and automatically retain the pedal in any selectedposition of tilted adjustment when pressure of the foot of the player isremoved therefrom, and also to insure smooth operation of the pedal.

Forwardly of bracket 11 and attached to plate 10 is a vertical metallicstop member 23 having at its upper end a resilient stop bumper 24 forlimiting tilting motion of the pedal in a clockwise directon betweensaid bumper 24 and aforementioned bumper 17.

In FIGS. 1, 2 and 3, a vertical rectangular panel board 25 of hardelectrical insulating material is situated forwardly of stop member 23and disposed transversely of plate 10 and supported by brackets 26, 26having bifurcated branches 26a attached to said plate by screw fasteningmeans 27 enabling adjustment of the board longitudinally of said plate.Fixed to the board is a hollow tubular light housing 28 open at bothends and formed of hard smooth surfaced plastic material havingelectrical insulating properties. The front of the housing is flanged asat 28a, and as shown in FIG. 2 the housing extends horizontally throughboard 25 with the flanged end thereof firmly secured against one side ofthe board by a fastening element at the opposite side of the board.

Telescopically received in said housing 28 are two interrelated hollowtubular members 29 and 30 of the same material as said housing. Thesemembers are nested partly within each other and firmly welded togetherto provided a substantiall integral rigid body adapted for freereciprocal motion in said housing. Member 29 forms a receptacle for alamp socket 31 having a bayonet slot 32 to receive the retaining stud32a of the aforementioned incandescent light bulb 34. The base of thelamp socket is contracted and passes through a U-shaped coupling member35 and is upset against wall 36 thereof enabling attachment of circuitlead wires W2 and W3 to the light bulb 34.

In FIG. 1 a motion imparting means consisting of a rigid steel rod M ispivoted at 37a to plate 14 of the expression pedal 12 and disposedforwardly of shaft 12b. The rod extends downwardly and forwardly, thelower end terminating in a trunnion M2 received in apertures M3 in thecoupling 35 and having one end freely engaged with a rail M4 fixedlymounted on base plate 10 of the expression pedal assembly. As shown, therail is disposed parallel to the axial center of housing 28. A coilretractile spring M1 has one end attached to base plate 10 so that thespring has a toggle motion in response to push and pull actuation ofsaid rod M enabling compensating to changes in tilting motion of saidpedal and whereby the free end of the trunnion is resiliently maintainedin operative riding engagement with said rail that uniform. reciprocalmotion is imparted to light bulb in a plane coaxial with said housing28.

Referring to FIG. 5, two photoresistors C are spaced apart from eachother, each adapted to be connected in a signal transmission andreproducing system substantially in the manner shown and described inthe description of FIG. 4. Coactive with both photoresistors forsimultaneous activation and deactivation thereof is a light sourceconsisitng of bulb 34 which is operable in the manner described in thedescription of FIG. 4.

Referring to FIG. 6, four photoresistors C are shown spaced apart fromeach other and arranged to form a circular group. Each photoresistor isadapted to be connected to a signal channel individual thereto andhaving an amplifier and associated electroacoustic transducer as setforth in the description of FIG. 4, the respective channels being commonto a light source 34 which we can assume is mounted for reciprocalmotion respectively into and out of the field of activating sensitivityof said photoresistors enabling converting the resistances thereof froma non-conductive electrical state into a variable conductive state inresponse to selected reciprocal motion of said light source. Theresistance of the photoresistors are of the same impedance value, thereason being that ordinarily, in each channel of a stereophonic organthe expression should be the same, i.e., about on the order of 25decibels.

Functionally, all of the several embodiments of the invention are thesame, the difference being merely in the number of tone signal channelsand interrelated light responsive devices in circuitry including one ormore reproducing systems, in each embodiment only a single light sourcebeing required for controllng activation of the light responsivedevices.

While we have shown and described several embodiments of the inventionrespectively diifering from each other only by the number of tone signalchannels and associated light responsive device, this is by way ofillustration as the number can be increased according to the type ofmusical instrument and the number of reproducing systems used as wouldbe the case in some stereophonic systems.

What we claim as our invention is:

1. A swell control for a musical instrument having a tone signal outputsystem and a signal reproducing system, said control comprising, aphotoresistor coupling the tone signal output system to the reproducingsystem, an incandescent light bulb of low voltage selectively movable ina housing enabling light of desired luminous intensity to activate thephotoresistor and thereby control conduction of the signal output tosaid reproducing system, and a panel board at one side of which thephotoresistor is mounted and at the other thereof the housing is mountedand opens onto the light exciting field of the photoresistor.

2. A swell control according to claim 1 wherein the housing, the panelboard and the light bulb are all thereof elements of a swell pedalassembly having motion imparting means responsive to operation of thepedal of said assembly for moving the light bulb between two linearlyspaced apart positions in said housing.

3. A swell control according to claim 2 wherein there is included insaid assembly means for maintaining the pedal in any desired position oftilted adjustment.

References Cited UNITED STATES PATENTS 1,956,350 4/1934 Hammond 84--1.27X 2,822,429 2/1958 Watson 179100.3 3,318,991 5/1967 Cookerly et al84-1.27 X 3,374,316 5/1968 Slaats et a1 841.27 X

WARREN E. RAY, Primary Examiner U.S. Cl. X.R. 841.27; 250-234

